The underlying hypothesis of this funded grant is that knowledge of the genes that can suppress apoptosis in thymocytes and cancer cells overexpressing BCL-2, after treatment with radiation or drugs that induce DNA damage, will implicate relevant, and drug targetable, pathways through which BCL-2 exerts its anti-apoptotic activity. As part of the two aims of the original parent proposal, a forward genetic screen was conducted and outstanding progress has been made identifying novel mutants that suppress BCL-2 following DNA damage. During the course of these studies, unexpected and exciting new findings were made indicating that a less studied apoptotic pathway triggered by Endoplasmic Reticulum (ER) stress can identify a completely different set of targets that can mediate suppression of the anti-apoptotic BCL-2 pathway. Thus, we are submitting this competitive revision application to add a new research aim for our grant to exploit the promising ER stress-induced apoptotic pathway as a mechanism to sensitize and kill BCL-2-overexpressing cancer cells. Remarkably, our preliminary studies show that ER stress can selectively kill T-cells in zebrafish larvae independent of BCL-2 status and we already have convincing preliminary data that establishes the zebrafish as a powerful new vertebrate model system for dissecting the molecular mechanisms of ER stress-induced apoptosis. We propose the following New Aim 3: To identify and analyze critical genes that modulate ER stress-induced apoptosis in the context of overexpressed BCL-2 during zebrafish embryogenesis and in zebrafish models of T-ALL. Due to our significant progress in preliminary studies establishing critical assay systems and reagents, we are 'shovel ready'to make major advances on this new Aim through experiments that can definitely be completed within the one and one-half year time-frame of this ARRA stimulus mechanism. In accomplishing this aim, the embryonic role of pro-apoptotic BH3-only proteins in ER stress will be established, two novel ER stress enhancer mutants that we already have recovered will be genetically mapped and analyzed, and the effects of ER stress enhancer mutations on ER-stressed T-ALL cells will be determined. In order to accelerate the conduct of these proposed studies we urgently need funding to retain Dr. Ujwal Pyati, a postdoctoral fellow currently supported on an NIH training grant that expires June 30, 2009, who developed our preliminary data on the zebrafish ER stress model. We also will immediately hire a qualified research technologist and order the supplies and reagents needed for our new experiments. These experiments will be completed and the papers describing these results will be submitted within 18 months of receipt of the funds supported by this competitive renewal application. PUBLIC HEALTH RELEVANCE: The discovery of BCL-2 suppressor mutations will identify pivotal targets whose inhibition by antibodies or small molecules will restore normal cell death pathways, thus enhancing the effectiveness of apoptosis-inducing therapies for B-cell follicular lymphoma and other BCL-2-overexpressing apoptosis-resistant cancers in humans.